4-1BB Receptor (CD137, 4-1BB Ligand Receptor, TNFRSF9, CDw137, ILA, MGC2172, T-cell antigen 4-1BB homolog) (PE)

4-1BB is an inducible T cell surface protein belonging to the TNF receptor superfamily. It is alternatively known as TNFRSF9, CD137, and ILA. The 255aa human 4-1BB is a type I transmembrane protein having in its extracellular domain four of the cysteine-rich motifs that are characteristic of the TNF receptor superfamily. The 30 KD glycoprotein exists both as a monomer and as a dimer on T cells. The human and mouse proteins share 60% aa identity. 4-1BB is absent from naive T cells, but it is upregulated and continually expressed following T cell activation. The natural ligand, 4-1BBL, is a member of the TNF superfamily and is expressed on activated antigen presenting cells including dendritic cells, macrophages, and B cells. Cross- linking of 4-1BB by 4-1BBL or by agonistic antibodies transmits a potent co-stimulatory signal that enhances the effect of other activating signals such as PHA or anti-CD3 antibodies. 4-1BB signals through the TFAF2-NIK pathway resulting in activation of NF-kB and ultimately promoting proliferation and survival of T cells. For recent reviews on 4-1BB see Vinay, D. and B. Kwon, 1998, Semin. Immunol. 10:481 and Sica, G. and L. Chen, 2000 Adv. Exp. Med. Biol. 465:355. Applications: Suitable for use in Flow Cytometry. Other applications not tested. Recommended Dilution: Flow Cytometry: Designed to quantitatively determine the percentage of cells bearing 4-1BB Ligand/TNFSF9 within a population and qualitatively determine the density of 4-1BB Ligand/TNFSF9 on cell surfaces by flow cytometry. Washed cells are incubated with the phycoerythrin-labeled monoclonal antibody, which binds to cells expressing 4-1BB Ligand/TNFSF9. Unbound phycoerythrin-conjugated antibody is then washed from the cells. Cells expressing 4-1BB Ligand/TNFSF9 are fluorescently stained, with the intensity of staining directly proportional to the density of expression of 4-1BB Ligand/TNFSF9. Cell surface expression of 4-1BB Ligand/TNFSF9 is determined by flow cytometric analysis using 488nm wavelength laser excitation and monitoring emitted fluorescence with a detector optimized to collect peak emissions at 565-605nm. Storage and Stability: May be stored at 4 degrees C for short-term only. For long-term storage and to avoid repeated freezing and thawing, aliquot and store at -20 degrees C. Aliquots are stable for at least 12 months at -20 degrees C. For maximum recovery of product, centrifuge the original vial after thawing and prior to removing the cap. Further dilutions can be made in assay buffer.